Field of the Invention
The invention relates to a method for controlling a winding station of a bobbin winding machine when a take-up bobbin is changed, which includes driving the take-up bobbin by contact with a yarn guide drum depositing a yarn, and bringing the take-up bobbin to a standstill when a predetermined quantity of yarn is reached. The invention also relates to a winding station for carrying out the method.
In present-day bobbin winding machines, changing the take-up bobbins, which as a rule are cylindrical or conical cross-wound bobbins and are also known as cheeses, is performed automatically by a changer unit. In order to perform the changing process, the take-up bobbin must first come to a standstill. Moreover, yarn travel must not be interrupted during the change. If the standstill once a desired or predeterminable quantity of yarn has been wound up is to be achieved, then the actual yarn quantity must be checked constantly, so that the attainment of the specified yarn quantity can be detected.
In German Patent No. 608 025, the present diameter of the take-up bobbin is determined through deflection of a creel. When a specified yarn quantity, in that case the specified diameter, is reached, a drive drum is braked sharply through mechanical switch elements and a friction coupling. That can not only damage the surface of the bobbin but can also cause yarn to be knocked off the bobbin.
In order to prevent such an occurrence, it has been proposed in German Published, Non-Prosecuted Application DE 32 13 631 A1 that only the drive mechanism be shut off, and that the yarn guide drum with the take-up bobbin resting on it be allowed to come to a stop. That process of slowing to a stop takes a relatively long time because of the inertia of the rotating packages. Moreover, in that phase of slowing to a stop, the synchronized travel of the yarn guide drum and the take-up bobbin in terms of their circumferential speed can cause ribboning, which causes considerable problems in subsequent processing of the take-up bobbin. Moreover, the relatively long rundown time, which is dictated by inertia, causes differences in the length of yarn being wound up. That in turn leads to yarn remnants when the take-up bobbins are later paid out jointly from the same creel.
In order to avoid those disadvantages, German Published, Non-Prosecuted Application DE 36 11 263 A1, which defines a generic method and apparatus from which the invention begins, proposes cutting the traveling yarn when the specified yarn length is reached, lifting the take-up bobbin from the yarn guide drum, braking the two rotating packages separately, and then joining the yarn ends again and briefly starting up the winding station again. In that way, the wound-up quantity of yarn is adjusted very precisely, and ribboning is also avoided. However, a disadvantage thereof is that when the take-up bobbin is later unwound, for instance from a creel on which it is mounted, all of the yarn joining stations are unwound at the same time. That can cause a visible flaw in a fabric made from it.